1. Field of the Invention
The present invention relates to a system and method for monitoring surge protectors. More specifically, the present invention relates to a system and method for monitoring each surge experienced by a surge protector, such as a metal oxide varistor (MOV), and generating a cumulative history to determine the remaining life of the protector.
2. Description of the Related Art
Surge suppressors include any number of devices that are designed and positioned in an electrical circuit to protect sensitive electronic and electrical equipment from high energy voltage transients. As known to those skilled in the art, many electrical devices are susceptible to high voltage surges, and accordingly, surge suppressors are provided to protect the devices from the harm that such surges can cause. Surge suppressors themselves can be comprised of a number of configurations, for example, inductor/capacitor networks, avalanche diodes, and so forth. However, these devices vary in speed, size, cost effectiveness, and energy handling capability.
Metal oxide varistors (MOVs) and silicon avalanche diodes (SADs) are two devices which are frequently used because they have exceptional speed, size, cost effectiveness, and energy handling capabilities. However, MOVs tend to wear down with each transient voltage event until they eventually fail. When either of these devices fails, there can be potentially deleterious results.
The most common method of controlling the potentially deleterious results of a suppressor failure is to place a fuse in series with the suppressor. The fuse is positioned and configured to open the circuit of the surge suppressor when the suppressor conducts a high current for long periods of time. Various methods of detecting that the fuse is blown are then used to provide a warning signal to the user that the suppressor is no longer functioning properly.
Another conventional method of controlling the potentially deleterious results of a suppressor failure incorporates a low melting point solder that eventually melts due to the heat generated by the failing suppressor. When the solder melts, the suppressor circuit is interrupted, thereby disconnecting the failed suppressor. However, under some circumstances, the solder will not melt quickly enough and significant heat, smoke and possible explosion can be produced during the delay. Further, this method does not react to high currents quickly. This results in the requirement of an additional fuse for this purpose, which increases expense and consumes space.
These conventional methods of detecting failures of suppressors have a major drawback in that they only alert a user of a failure of the suppressor, and do not provide indication of remaining suppressor service life. In doing so, after the suppressor fails, the load has no protection from high voltage transients. Many users of surge suppression devices do not often check their surge suppressors, thereby further extending the periods wherein the load is not protected from transient voltages. During these periods, the system is unprotected and the probability of failure of the load increases dramatically. Accordingly, there has been a need for systems and methods for the improved detection of suppressor failures.
One method of detecting when the load is close to being unprotected from high voltage transients is to have several suppressors connected in parallel with one another, wherein each parallel suppressor includes a fusing element. This method subjects every suppressor in the device to every high voltage transient that is on the line. The device detects when each suppressor fails and then indicates that the load is getting close to being unprotected by the reduced number of suppressors still functioning properly. This method is effective at giving early indication of the cumulative failure of a plurality of suppressors. However, there are drawbacks to this method besides the additional cost of using plural suppressors, fuses and detection circuits. Because the suppressors are in parallel and all are subjected to high voltage transients, all of the components are degraded together. This means that the amount of remaining protection available is variable and it is difficult to predict when the load will become unprotected. Further, this method is most effective with a plurality of suppressors, and is not suited for giving an early indication of the failure of a single suppressor.
Still other methods provide additional visual indications. For example, such a technique is disclosed by U.S. Pat. No. 5,748,093, to Swanson et al., and related U.S. Pat. No. 5,790,359, to Kapp et al., the entire disclosure of both being incorporated herein by reference. The above patents each disclose a surge protection system having a means for generating a visual indication of the level of surge protection, taking into account measured voltage values. The '093 and '359 patents disclose a means for sensing and storing data relating to voltage conditions in a nonvolatile memory, and determining an amount of surge protection remaining based on voltage readings. Specifically, in an example where a surge protector module includes four surge protection devices, a weighted average voltage is calculated and compared with four separate threshold values. The comparison is used to provide an output indication of a percentage surge protection remaining (that is, 100% where all four devices are functioning, 75% where three are functioning, 50% where two are functioning, and 0% where none are functioning) for the module via a display window. However, as with other conventional methods, this method is most effective with a plurality of suppressors and is not suited for giving an early indication of the failure of a single suppressor.
The above conventional methods are typically limited to determining if the continuity of an element such as a fuse, is intact or broken due to device failure, and notice is provided to a user regarding the status. Estimations of “remaining suppressor protection” is limited to cases wherein a plurality of suppressors exist and failures of each are detected.
Accordingly, a need exists for a system and method for effectively and efficiently estimating remaining suppressor protection levels in cases of even single devices, wherein values can be determined without reaching a point of suppressor failure.